Electronic blasting systems are widely used in mining and exploration to provide highly accurate controlled explosive blasts and blast patterns.
In blasting applications, conventional electronic detonators can communicate with a blasting control system, e.g., a blasting machine, using wired or wireless communication links. In existing blasting wireless systems, the wireless leg of the command path is often above the ground so that radio signals can be passed from the blasting machine to the above-ground wireless receivers and from there via a wire into the borehole to an electronic initiation device in the borehole. In such cases, two-way communication between the blasting machine and in-hole electronics allows diagnostic apparatuses external to the borehole to interrogate an in-hole device as to its condition. Such two-way communication may allow the condition of the in-hole device to be tested, and any instructions (e.g., a timing delay) that have been sent to the in-hole device to be confirmed (e.g., using a cyclic redundancy check).
A method of communication between an in-hole electronic initiation device and a blasting machine has been proposed using magnetic signals and magnetic sensors; however, magnetic-field-based systems for blasting typically need relatively large, high-powered transmission equipment to generate magnetic field fluctuations of sufficient strength to communicate with in-hole devices across a typical blasting field: for example, several hundred meters. It may be practical to provide sufficiently powerful transmitting equipment for a blasting machine above the ground or within underground access areas; however, it is not generally practical to provide an in-hole device with the necessary antenna and power to communicate back to a blasting machine using a magnetic signal. Accordingly, once an in-hole unit has been deployed, the above-ground portions of the magnetic system may not be able to discover the status or condition of the in-hole units, or confirm that an in-hole unit has correctly received information sent to it.
It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative.